At the present time, the American Society for Testing Materials (ASTM) has three standard tests for concrete pipe sewer lines. According to ASTM test C969-82 (Reapproved 1987) a length of sewer pipe no greater than 700 feet can be tested by either infiltration or exfiltration methods. In both of these tests, care must be taken to properly plug and seal the ends of the sewer pipe and all connections to the sewer pipe. For the infiltration test, if ground water conditions permit, the amount of water leaking into the sewer line is measured, and the rate of infiltration is determined. If the rate is less than or equal to the allowable limit, the section of sewer pipe tested is acceptable.
For the exfiltration test, the sewer line is filled with water to the recommended test head and the rate of water loss is determined. If the rate is less than or equal to the allowable limit, the section of sewer pipe tested is acceptable.
In both the infiltration and exfiltration tests, the ground water conditions around the pipe have a material affect on the test. Also, in exfiltration tests, an extended period of time is required for the pipe itself to stop absorbing water before the test can be carried out. In each of these tests, if a section of pipe fails, a difficult problem is presented in how to repair either the material making up the pipe or the joint in the pipe that is leaking.
The American Society for Testing Materials also has a low pressure air test method to demonstrate the integrity of the installed material and the construction procedures. This practice is used for testing 4 to 24 inch circular concrete pipe sewer lines utilizing gasketed joints. The ASTM designation for this test is C924-89. Great care must be taken with this test to properly prepare the pipe. The ends of the pipe have to be plugged and sealed to prevent any leakage. The seals must also be able to withstand the pressure so as not to be blown out. Even though only three to five pounds of air pressure is used in the test, this can be a dangerous procedure. Also, a large enough air compressor is required for the test to supply the volume of air needed. In the test, the sealed pipe is pressurized and the length of time it takes for the pressure to drop a predetermined amount is used to determine the integrity of the pipe.
The ASTM also has a standard test designation C1103-89 for the joints in installed precast pipe sewer lines. This test is usually used with large precast concrete pipe. The pipe must be large enough for the equipment used to carry out the test and for workers to set up the equipment. In the test, a ring is assembled and positioned internally about the joint in the pipe. A pair of inflatable sealing members near each edge of the ring are inflated, forming an annular space inside the ring. The space can then be filled with air or water and, if the rate of loss of the air or water through the joint is equal to or less than a predetermined amount, the joint is acceptable. If the joint leakage is greater than the predetermined amount, steps must then be taken to repair the joint. This test is typically a "go/no go" test.
None of the previous tests provide a convenient means for testing each pipe joint in a large precast sewer pipe after it has been assembled in a "test-as-you-go" method. Even in the test employing the ring with the inflatable seals, a substantial amount of time is lost in assembling, testing, disassembling and then moving on to the next joint.